Light Emitting Diode (LED) is a semiconductor light-emitting device fabricated by adopting P-N junction electro-luminescence principle. Advantaged at environmental protection, high luminance, low power consumption, long service life, low working voltage and easy integration, the LED is the fourth-generation new light source following incandescent lamp, fluorescent lamp and high intensity discharge lamp (HID).
Conventional LED package structure is made through die bond, bonding wire and fluorescent glue packaging on a metal support. In recent years, flip-chip scale package becomes popular as it requires neither substrate nor bonding wire where fluorescent glue is directly covered on the chip before cutting. With large radiant angle, this package is applicable for LED bulbs. However, large radiant angle is disadvantaged in other applications like spotlight and back light.
In Chinese patent CN101872817, a light emitting diode package structure with a glue wall is provided, comprising a light emitting diode chip and a glue wall on a ceramic substrate, and packaging glue covering the light emitting diode chip and the glue wall. In this structure, the glue wall is in an enclosed and circular shape to surround yet not contact with the light emitting diode chip. The glue wall is higher than the light emitting diode chip. Packaging glue made of transparent material is filled in the space between the light emitting diode chip and the glue wall. The package glue top has a convex surface for light condensing, and the convex surface edge aligns with the glue wall top. In this patent, the light emitting angle can be decided by the relative height difference and horizontal distance between the light emitting diode chip and the glue wall and no convex lens are additionally required, thus simplifying the entire package structure and improving reliability in actual operation. However, this method is disadvantaged in that: (1) the package structure needs to be installed on a large-size ceramic substrate, which prevents it from integration; (2) the vertical glue wall is not good for upward light emitting and affects light extraction efficiency.